This invention relates generally to the production of film and, more particularly, to the winding of thin film into rolls of high quality.
Equipment for winding rolls from a continuous length of film is available and in use. It is known, for example, that a roll can be wound by advancing a thin, wide film to a driven roll and then pressing the film with a straight lay-on roll. As the winding roll builds, machine direction (MD) tension in inner, subsurface wraps is relaxed but there is no opportunity for lateral expansion of each wrap to its full width. As a consequence, MD ridges are formed by a buckling phenomenon. These ridges become set and present difficulties in achieving uniformity in subsequent coating, metallizing and laminating steps.